p38 and extracellular signal-regulated kinase mitogen-activated protein kinase pathways are required for nuclear factor-kappaB p65 transactivation mediated by tumor necrosis factor.
Interleukin-6 (IL-6) is a pleiotropic cytokine, which is involved in inflammatory and immune responses, acute phase reactions, and hematopoiesis. In the mouse fibrosarcoma cell line L929, the nuclear factor (NF)-kappaB plays a crucial role in IL-6 gene expression mediated by tumor necrosis factor (TNF). The levels of the activated factor do not, however, correlate with the variations of IL-6 gene transcription; therefore, other factors and/or regulatory mechanisms presumably modulate the levels of IL-6 mRNA production. Upon analysis of various deletion and point-mutated variants of the human IL-6 gene promoter coupled to a reporter gene, we screened for possible cooperating transcription factors. Even the smallest deletion variant, containing almost exclusively a NF-kappaB-responsive sequence preceding the IL-6 minimal promoter, as well as a recombinant construction containing multiple kappaB-motifs, could still be stimulated with TNF. We observed that the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 was able to repress TNF-stimulated expression of the IL-6 gene, as well as of a kappaB-dependent reporter gene construct, without affecting the levels of NF-kappaB binding to DNA. Furthermore, we clearly show that, using a nuclear Gal4 "one-hybrid" system, the MAPK inhibitors SB203580 and PD0980589 have a direct repressive effect on the transactivation potential of the p65 kappaB subunit. Therefore, we conclude that, in addition to cytoplasmic activation and DNA binding of NF-kappaB, the p38 and extracellular signal-regulated kinase MAPK pathways act as necessary cooperative mechanisms to regulate TNF-induced IL-6 gene expression by modulating the transactivation machinery.
Vanden Berghe
W
W
Laboratory of Molecular Biology, Flanders Interuniversity Institute for Biotechnology and University of Gent, B-9000 Gent, Belgium.
Plaisance
S
S
Boone
E
E
De Bosscher
K
K
Schmitz
M L
ML
Fiers
W
W
Haegeman
G
G
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004789:Enzyme Activation; D015850:Interleukin-6 / Q000235:genetics; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B / Q000235:genetics*; D051996:Transcription Factor RelA; D015533:Transcriptional Activation / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
D015850:Interleukin-6; D016328:NF-kappa B; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases